Transmissions are utilized in an automotive vehicle for the transmittal of torque from a driving means, such as an internal combustion engine, to the final drive, such as a differential for the driving wheels of the vehicle. A shift control apparatus is used to enable the operator of the vehicle to control a multiple speed, sliding gear manual transmission for a plurality of forward speed ratios and a reverse speed ratio, the shift control apparatus providing appropriate crossover positions for a shift stick actuated by the vehicle operator. Each crossover position selects a shift fork or the like, which may be moved longitudinally in opposite directions to engage either one or two speed ratios.
In a four speed transmission, one crossover position is used to select the first and second speed ratios, another the third and fourth speed ratios, and another the reverse speed ratio. Likewise, in a five speed transmission, one crossover position is used to select the first and second speed ratios, another the third and fourth speed ratios, and yet another the fifth and reverse speed ratios. More recently, it is desirable under certain conditions that vehicle transmissions have six forward speed ratios to provide a sufficient number of gear ratios to enable the operator of a vehicle to provide the torque required for a smooth transition through the gears and arrive at a desired final driving speed. In conventional five and six speed transmissions, a main shift rail and an auxiliary shift rail are provided with a linkage arrangement to couple the main and auxiliary shift rails and the reverse idler gear. The linkage mechanism normally requires two levers arranged in a complicated assembly and two cam devices which must be precisely coordinated, resulting in a linkage mechanism that is complex and expensive. More recent developments have simplified the linkage mechanism but an auxiliary shift rail is still necessary.